This invention relates to detection apparatus and has particular, but not exclusive, reference to conductivity probes for use in radiators.
With the tendency for motor vehicle engines to become more powerful, the water cooling system used to cool the engines have had to become more efficient and more reliable. With modern engines, a sudden loss of coolant can rapidly give overheating conditions which can lead to distortion and even destruction of the engine. It has been proposed, therefore, to have detection apparatus to detect the coolant water level so that a warning of a low water level can be given to the vehicle driver. Conventionally, these detectors have worked by having a probe which has a part of its length in the water and which is otherwise insulated from the body of the radiator. The coolant establishes an electrical path between the probe and the radiator and this electrical path is monitored to indicate the presence of coolant water. Once the coolant level drops below the level of the probe, the electrical path is broken and this can be detected and used to give a warning to the driver.
It has been discovered, however, that certain types of radiators, and particularly cross-flow radiators, can have their header tanks full of froth even when the water level is below that which would normally cause the detection apparatus to indicate a low water level. This froth is normally created by the water pump which circulates the water through the engine and radiator and the froth can provide a sufficiently conducting electrical path between the probe and the radiator so that no warning is given to the driver. The froth does not, however, act as an efficient coolant and overheating and possible damage to the engine can occur without the driver being aware of the loss of coolant.